Devices currently exist that can track the movement of a person's eyes as that person engages in an activity, for example, using a computer system. Eye tracking devices generally consist of a camera and associated electronic components to produce data representing gaze positions (or “gaze data”). This gaze data can be used to determine where the individual is looking, which can be described in terms of fixations (a steady gaze for a predetermined period of time) and saccades (movement of the gaze between two points).
When the gaze data is combined with data representing graphical images presented to the user, the combined data indicates what the person was viewing (or “viewing data”). The viewing data can be used, for example, to determine whether a viewer has looked at all of the information presented. The viewing data is typically presented graphically as a series of circles and lines indicating the fixations and saccades, respectively. One disadvantage of typical viewing data and graphical representations of the viewing data is that only the viewing of a single user can be presented.